<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
<button id="btn">点击</button>    
<script>
        function fn(str){
        console.log(str)
    }
    btn.onclick = function (){
        const script = document.createElement("script")
        script.src = "http://localhost:5000/test?callback=fn"
        document.body.appendChild(script)
    }
</script>
</body>
</html>